Heavy Equipment Operator Certification Exam Prep · Question
When using a vibratory compactor on an embankment built with 200 mm lifts of silty clay, why might an operator choose to reduce the amplitude as compaction progresses through the passes?
Reducing amplitude on later passes helps prevent over-compaction, which can damage the soil structure, cause deep ruts, or lead to excessive energy use without
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Question: When using a vibratory compactor on an embankment built with 200 mm lifts of silty clay, why might an operator choose to reduce the amplitude as compaction progresses through the passes?
Answer options:
- To increase the speed of the compaction operation ✅ To prevent over-compaction and potential over-stressing of the already densified material
- To allow the engine to run at a lower RPM, saving fuel
- To make the machine easier to steer on the compacted surface
Correct answer: To prevent over-compaction and potential over-stressing of the already densified material
Explanation: Reducing amplitude on later passes helps prevent over-compaction, which can damage the soil structure, cause deep ruts, or lead to excessive energy use without further density gain. It's often adjusted with increasing stiffness.
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